Memory systems for phased garbage collection using phased garbage collection block or scratch pad block as a buffer

ABSTRACT

A non-volatile memory storage system is provided. The non-volatile memory storage system comprises a memory configured to store a storage system firmware and a non-volatile memory cell array. Additionally included is a processor in communication with the memory and the non-volatile memory cell array. The processor is configured to execute the storage system firmware stored in the memory. The storage system firmware includes program instructions for receiving a write command to write a plurality of data to the non-volatile memory cell array. The write command is allocated a timeout period to complete an execution of the write command. Additionally included are program instructions for asserting a busy signal, performing a portion of a garbage collection operation for a garbage collection time period, writing the data to a block, and releasing the busy signal before the timeout period.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.11/541,035, filed on Sep. 28, 2006, and entitled “Methods for PhasedGarbage Collection Using Phased Garbage Collection Block or Scratch PadBlock as a Buffer;” is related to U.S. patent application Ser. No.11/040,325, filed on Jan. 20, 2005, and entitled “Scheduling ofHousekeeping Operations in Flash Memory Systems;” is related to U.S.application Ser. No. 11/499,606 , filed on Aug. 4, 2006, and entitled“Methods for Phased Garbage Collection;” and is related to U.S. patentapplication Ser. No. 11/499,598 , filed on Aug. 4, 2006, and entitled“Non-Volatile Memory Storage Systems for Phased Garbage Collection,” thedisclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to memory operations and, moreparticularly, to methods and systems for performing phased garbagecollection operations.

BACKGROUND

In non-volatile memory storage systems, blocks of data stored in thememory are periodically garbage collected (i.e., compacted orconsolidated) to reclaim a memory's storage capacity. In a typicalgarbage collection operation, valid data from a block are copied toanother block. After the valid data are transferred, the original blockis erased to provide storage capacity. Currently, a write operation cantrigger a non-volatile memory storage system to perform a garbagecollection operation. The host allows a fixed amount of time for theexecution of the write operation, which includes the garbage collectionoperation, if triggered. For example, the Secure Digital protocol limitsthe amount of time to 250 milliseconds. A timeout error can result ifthe non-volatile memory storage system exceeds this fixed amount of timein a write operation.

The sizes of memory blocks have been increasing due to increasedcapacity, higher parallelism, and die size scaling. Accordingly,executions of write operations are taking longer because more data aretransferred. A garbage collection operation can therefore easily exceedthe fixed amount of time allocated to the write operation. As a result,there is a need to prevent the timeout errors when the amount of time toperform a garbage collection operation exceeds the fixed amount of time.

SUMMARY

Various embodiments of the present invention provide methods and/orsystems for phased garbage collection operations. It should beappreciated that the embodiments can be implemented in numerous ways,including as a method, a circuit, a system, or a device. Severalembodiments of the present invention are described below.

In an embodiment, a non-volatile memory storage system is provided. Thenon-volatile memory storage system comprises a memory configured tostore a storage system firmware and a non-volatile memory cell array.Additionally included is a processor in communication with the memoryand the non-volatile memory cell array. The processor is configured toexecute the storage system firmware stored in the memory. The storagesystem firmware includes program instructions for receiving a writecommand to write a plurality of data to the non-volatile memory cellarray. The write command is allocated a timeout period to complete anexecution of the write command. Additionally included are programinstructions for asserting a busy signal, performing a portion of agarbage collection operation for a garbage collection time period,writing the data to a block, and releasing the busy signal before thetimeout period.

Other embodiments and advantages of the invention are apparent from thefollowing detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings, andlike reference numerals designate like structural elements.

FIG. 1 is a simplified block diagram of an example of a non-volatilememory storage system, in accordance with an embodiment of the presentinvention.

FIG. 2 is a simplified block diagram of an organization of the memorycell array into planes.

FIG. 3 is a simplified block diagram of pages of memory cells.

FIG. 4 is a simplified block diagram of sectors of memory cells.

FIG. 5 is a simplified block diagram of a logical interface between ahost and a non-volatile memory storage system.

FIG. 6 is a flowchart diagram of a general overview of operations forphased garbage collection, in accordance with an embodiment of thepresent invention.

FIG. 7 shows a simplified block diagram of an example of one garbagecollection operation split into multiple portions, in accordance with anembodiment of the present invention.

FIG. 8 is a flowchart diagram of detailed operations for performing aphased garbage collection with the use of a phased garbage collectionblock as a buffer, in accordance with an embodiment of the presentinvention.

FIGS. 9A and 9B are simplified block diagrams of memory blocks withsequential update blocks being garbage collected in phases, inaccordance with embodiments of the present invention.

FIGS. 10A and 10B are simplified block diagrams of memory blocks withchaotic update blocks being garbage collected in phases, in accordancewith an embodiment of the present invention.

FIGS. 11A, 11B, 11C, 11D, and 11E are simplified block diagrams ofmemory blocks with chaotic update blocks being garbage collected inphases, in accordance with another embodiment of the present invention.

FIG. 12 is a flowchart diagram of detailed operations for performing aphased garbage collection with the use of a scratch pad block as abuffer, in accordance with an embodiment of the present invention.

FIGS. 13A and 13B are simplified block diagrams of memory blocks withsequential update blocks being garbage collected in phases, inaccordance with embodiments of the present invention.

FIGS. 14A and 14B are simplified block diagrams of memory blocks withchaotic update blocks being garbage collected in phases, in accordancewith embodiments of the present invention.

FIG. 15 is a flowchart diagram of non-volatile memory storage systemoperations associated with a write command, in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION

A detailed description of one or more embodiments is provided belowalong with accompanying figures. The detailed description is provided inconnection with such embodiments, but is not limited to any particularembodiment. The scope is limited only by the claims and numerousalternatives, modifications, and equivalents are encompassed. Numerousspecific details are set forth in the following description in order toprovide a thorough understanding. These details are provided for thepurpose of example and the described embodiments may be implementedaccording to the claims without some or all of these specific details.For the purpose of clarity, technical material that is known in thetechnical fields related to the embodiments has not been described indetail to avoid unnecessarily obscuring the description.

The embodiments described herein provide methods and/or systems forphased garbage collection. In general, a garbage operation can be splitinto multiple phases. The phases (or portions) of the garbage collectionoperation can be performed over multiple timeout periods. As will beexplained in more detail below, a portion of a garbage collectionoperation is performed within one timeout period and the data receivedfrom the write command may be stored in a phased garbage collectionblock or a scratch pad block.

FIG. 1 is a simplified block diagram of an example of a non-volatilememory storage system, in accordance with an embodiment of the presentinvention. A host system (e.g., desktop computers, audio players,digital cameras, and other computing devices) may write data to and readdata from non-volatile memory storage system 102. Non-volatile memorystorage system 102 may be embedded within the host or removablyconnected to the host. As shown in FIG. 1, non-volatile memory storagesystem 102 includes memory controller 110 in communication with memory118. In general, memory controller 110 controls the operation of memory118. Examples of operations include writing (or programming) data,reading data, erasing data, verifying data, attending to garbagecollection operations, and other operations. Memory controller 110includes bus 124 that interfaces with system bus 126 through hostinterface 104 and the memory controller interfaces with memory 118through memory interface 108. Host interface 104, processor 106 (e.g.,microprocessor, microcontrollers, and other processors), memoryinterface 108, random access memory (RAM) 112, error correcting code(ECC) circuit 114, and read-only memory (ROM) 116 are in communicationby way of bus 124. ROM 116 can store a storage system firmware thatincludes program instructions for controlling the operation of memory118. Processor 106 is configured to execute the program instructionsloaded from ROM 116. The storage system firmware may be temporarilyloaded into RAM 112 and additionally, the RAM may be used to buffer datathat are transferred between a host and memory 118. ECC circuit 114 cancheck for errors passing through memory controller 110 between the hostand memory 118. If errors are found, ECC circuit 114 can correct anumber of error bits, the number depending on the ECC algorithmutilized.

Memory 118 can include array logic 120, non-volatile memory cell array122, and memory cell array 123. Non-volatile memory cell array 122 mayinclude a variety of non-volatile memory structures and technologies.Examples of non-volatile memory technologies include flash memories(e.g., NAND, NOR, Single-Level Cell (SLC/BIN), Multi-Level Cell (MLC),Divided bit-line NOR (DINOR), AND, high capacitive coupling ratio(HiCR), asymmetrical contactless transistor (ACT), and other flashmemories), erasable programmable read-only memory (EPROM),electrically-erasable programmable read-only memory (EEPROM), read-onlymemory (ROM), one-time programmable memory (OTP), and other memorytechnologies.

In an embodiment, memory 118 may additionally include memory cell array123 that is configured to store a buffer. The buffer is configured tostore data in a phased garbage collection operation. As will beexplained in more detail below, in a phased garbage collectionoperation, new data received from a write command can be stored in thebuffer. It should be appreciated that the buffer also may be located inRAM 112 or in non-volatile memory cell array 122, in accordance withembodiments of the present invention. Similar to non-volatile memorycell array 122, memory cell array 123 may include a variety of memorystructures and technologies. Since memory cell array 123 is configuredfor buffering operations, the memory cell array may incorporate adifferent memory structure or use different parameters that may befaster, more economical, and more reliable than non-volatile memoryarray 122.

Array logic 120 interfaces memory controller 110 with non-volatilememory cell array 122 and memory cell array 123 and can provide, forexample, addressing, data transfer and sensing, and other support to thenon-volatile memory cell array and the memory cell array. To supportnon-volatile memory cell array 122 and memory cell array 123, arraylogic 120 can include row decoders, column decoders, charge pumps, wordline voltage generators, page buffers, input/output buffers, addressbuffers, and other circuitries.

FIG. 2 is a simplified block diagram of an organization of the memorycell array into planes. One or more memory cell arrays may be dividedinto multiple planes or sub-arrays. In the example of FIG. 2, a memorycell array is divided into four planes 202-205. It should be appreciatedthat other number of planes, such as 1, 2, 8, 16, or more, can exist ina non-volatile memory storage system. Each plane 202, 203, 204, or 205may be divided into blocks of memory cells, such as blocks 210-213 and220-223, located in respective planes 202-205. A block of memory cellsis the smallest number of memory cells that are physically erasabletogether. For increased parallelism, the blocks can be operated inlarger metablock units where one block from each plane 202, 203, 204, or205 is logically linked together to form a metablock. For example, fourblocks 210-213 can be logically linked together to form a metablock.Further, the blocks used to form a metablock can be from variouslocations within their respective planes, such as planes 202-205. Forexample, four blocks 220-223 from various locations within theirrespective planes 202-205 can be logically linked together to formanother metablock. A metablock may extend across all four logical planes202-205 within the non-volatile memory storage system or thenon-volatile memory storage system can dynamically form metablocks fromone or more blocks in one or more different planes.

FIG. 3 is a simplified block diagram of pages of memory cells. Eachblock, such as blocks 210-213, is further divided into pages of memorycells. As shown in FIG. 3, each block 210, 211, 212, or 213 is dividedinto eight pages P0-P7. Alternatively, there can be 16, 32, or morepages of memory cells within each block 210, 211, 212, or 213. Toincrease the operational parallelism of the non-volatile memory storagesystem, the pages within two or more blocks may be logically linked intometapages. For example, a metapage can be formed of one page, such asP1, from each of four blocks 210-213. A metapage can extend across allplanes within the non-volatile memory storage system or the non-volatilememory storage system can dynamically form metapages from one or morepages in one or more separate blocks in one or more different planes.

FIG. 4 is a simplified block diagram of sectors of memory cells. A pagecan be further divided into one or more sectors. The amount of data ineach page can be an integer number of one or more sectors of data, whereeach sector may store 512 bytes of data. FIG. 4 shows page 401 dividedinto two sectors 402 and 404. Each sector 402 or 404 contains data 406,which can be 512 bytes in size, and overhead data 405 associated withthe data. The size of overhead data 405 can be 16 bytes and can store,for example, an ECC calculated from data 406 during programming, thelogical address associated with the data, a count of the number of timesthe block has been erased and re-programmed, control flags, operatingvoltage levels, and other information associated with the data.

FIG. 5 is a simplified block diagram of a logical interface between ahost and non-volatile memory storage system. A continuous logicaladdress space 512 provides addresses for data that can be stored inmemory. Logical address space 512 as viewed by the host can be dividedinto increments of clusters of data. Each cluster may include a numberof sectors of data, such as between 4 and 64 sectors.

As shown in FIG. 5, an application program executed on the host createsthree data files 1, 2, and 3. Files 1, 2, and 3 can be an ordered set ofdata and are identified by a unique name or other reference. The hostassigns a logical address space to file 1 that is not already located toother files. Here, file 1 is shown to have been assigned a continuousrange of available logical addresses.

When host creates file 2 after file 1, the host similarly assigns twodifferent ranges of continuous addresses within logical address space512. Host may not assign a continuous logical address to a file, such asfile 1, 2, or 3, but can rather assign fragments of logical addresses inbetween logical address ranges already allocated to other files. Theexample of FIG. 5 shows that another file 3 is allocated anon-continuous address range within logical address space 512, which isnot previously allocated to files 1 and 2 and other data.

The host can keep track of logical address space 512 by maintaining afile allocation table (FAT), where the logical addresses assigned by thehost to the various data files, such as files 1-3, by conversion aremaintained. The host references files 1-3 by their logical addresses andnot by the physical locations where the non-volatile memory storagesystem stores the files. On the other hand, the non-volatile memorystorage system references files 1-3 by portions of the logical addressesto which data have been written and does not reference the files by thelogical addresses allocated to the files. The non-volatile memorystorage system converts the logical addresses provided by the host intounique physical addresses within memory cell array 502 where data fromthe host are stored. Block 504 represents a table of theselogical-to-physical address conversions, which is maintained by thenon-volatile memory storage system.

FIG. 6 is a flowchart diagram of a general overview of operations forphased garbage collection, in accordance with an embodiment of thepresent invention. It should be appreciated that data stored at specifichost logical addresses can be overwritten by new data as the originalstored data become obsolete. The non-volatile memory storage system, inresponse, writes the new data in an update block and then changes thelogical-to-physical address table for those logical addresses toidentify the new physical block to which the new data are stored. Theblocks containing the original data at those logical addresses are thenerased and made available for the storage of additional data. Sucherasure can take place before a write operation. As a result, the memorycontroller learns that data at a given logical address have beenrendered obsolete or invalid by the host after the new data are writtento the same logical address. Many blocks of memory can therefore bestoring invalid data for a period of time.

The sizes of blocks and metablocks are increasing and such increasesresult in a large proportion of individual data writes storing an amountof data that is less than the storage capacity of a metablock, and inmany instances, even less than that of a block. Since the non-volatilememory storage system can direct new data to an erased pool metablock,such direction can result in portions of blocks or metablocks beingunfilled. If the new data are updates of some data stored in anothermetablock, remaining valid metapages of data from that other metablockhaving logical addresses contiguous with those of the new data metapagesare also copied in logical address order into the new metablock. The oldmetablock may retain other valid data metapages. Accordingly, data ofcertain metapages of an individual metablock can be rendered obsolete orinvalid, and replaced by new data with the same logical address beingwritten to a different metablock.

In order to maintain enough physical memory space to store data over alogical address space, such data can be periodically garbage collected(i.e., compacted or consolidated). In general, a garbage collectionoperation involves reading the valid data from a block and writing thevalid data to a new block, ignoring invalid data in the process. Forexample, in the block diagram of FIG. 5, the creation of new data file 3makes old data file 3 obsolete. Old data file 3 can be erased to reclaimthe physical capacity used by old data file 3. However, such eraseoperation would trigger a garbage collection operation if file 2 and oldfile 3 are stored in the same physical block.

Returning to FIG. 6, the non-volatile memory storage system may performthe garbage collection operation within a timeout period allocated to awrite command. If the garbage collection operation cannot be completedwithin one timeout period, then the one garbage collection operation maybe split into several different phases (or portions), in accordance withan embodiment of the present invention. Here, the non-volatile memorystorage system performs portions of the garbage collection operationusing the timeout periods allocated to multiple write commands. In otherwords, the non-volatile memory storage system utilizes the timeoutperiods allocated to multiple write commands to perform portions of onegarbage collection operation.

As shown in FIG. 6, a write command to write new data is received inoperation 602. As used herein, the term “new data” is defined as thedata received by the non-volatile memory storage system from a writecommand to be written to the memory. The write command is allocated atimeout period to complete the execution of the write command. In otherwords, the timeout period is a period of time allocated for an executionof the write command. An example of a timeout period allocated is 250milliseconds. The write command can be a single sector write command ora multiple sectors write command. As will be explained in more detailbelow, in a single sector write command, new data can be written assingle sectors to random addresses across a memory. In a multiplesectors write command, multiple sectors of new data having contiguous,logical addresses are written to the memory.

If one garbage collection operation cannot be completed within thetimeout period, as shown in operation 604, a portion of the garbagecollection operation is performed within the timeout period allocated tothe write command. The remaining portions of the garbage collection canbe completed at later timeout periods. For example, FIG. 7 shows asimplified block diagram of an example of one garbage collectionoperation split into multiple portions 780 and 781, in accordance withan embodiment of the invention. As shown in FIG. 7, a non-volatilememory storage system receives multiple sectors write command 704 andsubsequently, multiple sectors of new data 760-762 are received forstorage into memory. Busy signal 702 is asserted after each sector ofdata 760, 761, or 762 is received. The non-volatile memory storagesystem asserts busy signal 702 to allow the execution of the writecommand, which may include garbage collection operation (if needed), andother operations. A host does not send another command or additionaldata to the non-volatile memory storage system when busy signal 702 isasserted. The non-volatile memory storage system can assert busy signal702 for a limited amount of time after each sector of data 760, 761, or762 is received because the host allows a limited fixed amount of time(i.e., timeout periods 750-752) for the execution of the write command.If the busy signal remains active for longer than timeout period 750,751, or 752, the host may repeat the write command or abort the process.Accordingly, the non-volatile memory storage system cannot assert busysignal 702 for more than timeout period 750, 751, or 752. Releasing busysignal 702 after the completion of writing multiple sectors of data760-762 allows the host to communicate further with the non-volatilememory storage system.

Still referring to FIG. 7, portions 780 and 781 of the garbagecollection can be allocated between multiple timeout periods 750-752. Inother words, the non-volatile memory storage system can utilize eachtimeout period 750, 751, or 752 to perform each portion 780 or 781 ofone garbage collection operation. For example, first portion 780 of onegarbage collection is performed during first timeout period 750. Here, aportion of valid data can be copied from one block to another blockduring first timeout period 750. At second timeout period 751, theprevious garbage collection operation started at first timeout period iscontinued. The non-volatile memory storage system performs secondportion 781 of the previous garbage collection operation during timeoutperiod 751 until the previous garbage collection is completed. Theprevious garbage collection can be completed by copying the remaining orlast portion of the valid data from the one block to the other block. Ifthe previous garbage collection operation cannot be completed withinsecond timeout period 751, then the non-volatile memory storage systemcan use subsequent timeout periods, such as third timeout period 752, tocomplete the garbage collection operation. At the end of multiplesectors write command 704, the non-volatile memory storage system canassert busy signal 702 after stop command 706 is received until allsectors of data 760-762 are written to the memory cell array. It shouldbe noted that FIG. 7 illustrates the operations associated with amultiple sectors write command. As will be explained in more detailbelow, the garbage collection operations performed may be different forsingle sector write commands and multiple sectors write commands. Forexample, as will be explained in more detail below, the type of bufferused to store the new data may depend on whether the write commandreceived is a single sector write command or a multiple sectors writecommand.

Returning to FIG. 6, after a portion of the garbage collection operationis performed within a timeout period, the new data received from thewrite operation can be stored in a buffer associated with thenon-volatile memory storage system in operation 606. In an embodiment,the buffer may be a data structure associated with the non-volatilememory cell array (e.g., non-volatile memory array 122 shown in FIG. 1).An example of a data structure includes a block of the non-volatilememory cell array, such as a phased garbage collection block or ascratch pad block, which will be described in more detail below. Inanother embodiment, the buffer may be a block of a volatile memory cellarray. For example, the new data may be stored in a block located in theRAM associated with the non-volatile memory storage system (e.g., RAM112 shown in FIG. 1). In still another embodiment, as discussed above,the new data may be stored in a block located in a separate memory cellarray (e.g., memory cell array 123 shown in FIG. 1).

Use of a Phased Garbage Collection Block as a Buffer

FIG. 8 is a flowchart diagram of detailed operations for performing aphased garbage collection with the use of a phased garbage collectionblock as a buffer, in accordance with an embodiment of the presentinvention. As shown in FIG. 8, a write command is received in operation802 to write new data to a memory. As will be explained in more detailbelow, the write command may be a single sector write command to write asingle sector of data to the memory. After the write command isreceived, the non-volatile memory storage system asserts a busy signalin operation 804.

Before the write command is executed, a portion of the garbagecollection operation is performed for a garbage collection time period.For example, in an embodiment, one or more first blocks are selected fora garbage collection operation. The one or more first blocks can includeinvalid data and/or valid data. As shown in operation 806, the validdata are copied from the one or more first blocks to a second block fora garbage collection time period in the garbage collection operation.Depending on the garbage collection time period allocated to the garbagecollection operation and on the amount of valid data that are to becopied, all the valid data or a portion of the valid data are copied tothe second block. In an example, the garbage collection time periodallocated for the garbage collection operation can be expressed asGarbage collection time period=Timeout Period−2*Tprog  (1.0)where timeout period, as discussed above, is a fixed, limited period oftime. Tprog is the maximum programming time associated with writing thenew data to memory or is the maximum time the non-volatile memorystorage system takes to write the new data to the memory. In Equation1.0, there are two maximum programming times (i.e., 2*Tprog). As will beexplained in more detail below, the first maximum programming time isattributed to writing the new data to a third block and the secondmaximum programming time is attributed to writing the new data to ascratch pad block. As a result, in an embodiment, the non-volatilememory storage system tracks the amount of time for copying the validdata from the one or more first blocks to the second block. Thenon-volatile memory storage system stops the copy before the timeexceeds the garbage collection time period.

If the garbage collection operation cannot be completed by the garbagecollection time period, then the new data associated with the writecommand can be written to a phased garbage collection block in operation810. The non-volatile memory storage system can write the new data tothe phased garbage collection block before, during, or after the garbagecollection operation. The phased garbage collection block has thecharacteristics of an update block. In general, data received from awrite command may be written to an update block. A dedicated metablockcan be assigned as an update block for each logical group within whichdata are being updated. A logical group is a group of logical addresseswith a size that may equal to the size of a metablock. It should benoted that logical sectors of data are stored in logical groupscomprising a set of logically contiguous sectors. As will be explainedin more detail below, an update block can be managed to receive data ineither sequential order or chaotic order (i.e., non-sequential order).The phased garbage collection block may or may not be associated withthe one or more first blocks and the second block. For example, in anembodiment, the one or more first blocks, the second block, and thephased garbage collection block are configured to span a single logicalgroup or a single group of logical addresses. As a result, data from asingle logical group can be stored in the phased garbage collectionblock, but data from a different logical group cannot be stored in thephased garbage collection block.

After the new data are written to the phased garbage collection blockand the garbage collection operation is performed for the garbagecollection time period, the non-volatile memory storage system releasesthe busy signal before the timeout period in operation 812. Thus, thetotal time for executing the write command that includes one garbagecollection operation or a portion of one garbage collection operationdoes not exceed the timeout period. If a portion of the garbagecollection operation is performed within the timeout period, then theremaining portions are completed at subsequent timeout periods. When thegarbage collection operation is complete, the one or more first blocksbeing garbage collected are erased (or marked as obsolete) and madeavailable for the storage of additional data. Additionally, as will beexplained in more detail below, the phased garbage collection block canbe converted into an update block. Thereafter, another, new phasedgarbage collection block that replaces the phased garbage collectionblock, which was converted into an update block, may be allocated tostore new data from subsequent write commands in phased garbagecollection operations.

FIGS. 9A and 9B are simplified block diagrams of memory blocks withsequential update blocks being garbage collected in phases, inaccordance with embodiments of the present invention. As shown in FIG.9A, original block A 902 and associated sequential update block A 904are selected for garbage collection. An update block can be managed toreceive data in either sequential order or chaotic order (i.e.,non-sequential order). It should be appreciated that a sequential updateblock, such as sequential update block A 904, is a metablock allocatedwhen a write command is received from the host to write data that fillsone or more physical page in a logical group for which all valid sectorsare currently located in the same metablock. Sectors of data written tothe sequential update block are written sequentially in logicaladdressing such that the sectors supersede the corresponding logicalsectors written in the original block. A sector updated in this logicalgroup can be written to this sequential update block, until thesequential update block is either closed or converted to a chaoticupdate block. It should be noted that the sequential update block isconsidered closed when the last physical sector location of thesequential update block is written. In other words, closure of thesequential update block may result from the sequential update blockbeing completely filled by updated sector data written by the host orcopied from the original block. As will be explained in more detailbelow, the chaotic update block can be created by conversion from asequential update block when a sector of data written by a host islogically non-sequential to the previously written sector of data withinthe logical group being updated.

Original block A 902 can include invalid and valid data, which isrepresented in FIG. 9A by hatched pattern and dotted pattern,respectively. It should be noted that in addition to valid data fromoriginal block A 902, sequential update block A 904 additionallyincludes existing data 905 that were written to the sequential block Abefore the garbage collection operation. When a write command to writenew data 910 is received, the write command may trigger the closure ofsequential update block A 904, which is a type of garbage collectionoperation, because the new data are associated with a logical group thatis different from the sequential update block A. The non-volatile memorystorage system asserts a busy signal and then copies the valid data fromoriginal block A 902 to sequential update block A 904 until firstgarbage collection time period 906 is reached. During copying, thenon-volatile memory storage system tracks the time, and the non-volatilememory storage system stops the copy operation before first garbagecollection time period 906 is exceeded. As shown in FIG. 9A, the garbagecollection operation cannot be completed within first garbage collectiontime period 906 as there are still valid data remaining in originalblock A 902. As a result, after the portion of valid data are copied tosequential update block A 904, new data 910 are written to phasedgarbage collection block A 908 within the remaining time allowed beforefirst timeout period is reached.

FIG. 9B shows that the remaining portion of the garbage collectionoperation can be completed within a second timeout period. Here, asecond write command to write new data 918 is received after the firstwrite command. As a result, a second timeout period is allocated to thesecond write command. During the second timeout period, the remainingvalid data are copied from original block A 902 to sequential updateblock A 904. In this example, all the remaining valid data (or lastportion of the valid data) can be copied to sequential update block A904 within second garbage collection time period 912. Accordingly, thegarbage collection operation can be completed within the second timeoutperiod. Original block A 902 is erased and can be made available for thestorage of additional data because the garbage collection operation iscompleted in this second timeout period. Since sequential update block A904 is filled, the sequential update block A is converted to neworiginal block A 914 or a non-update block. Further, phased garbagecollection block A 908 is converted to an update block, such as updateblock B 916, that may or may not be associated with new original block A914. A new phased garbage collection block, such as phased garbagecollection block C 908, is also allocated to store new data. If new data918 from the second write command are from the same logical group as newdata 910, then the new data 918 from the second write command may bewritten to update block B 916. On the other hand, as will be explainedin more detail below, if new data 918 from the second write command arefrom a different logical group from new data 910, then the new data 918from the second write command are written to phased garbage collectionblock C 908.

FIGS. 10A and 10B are simplified block diagrams of memory blocks withchaotic update blocks being garbage collected in phases, in accordancewith an embodiment of the present invention. As shown in FIG. 10A,original block A 1002 and chaotic update block A 1004 are selected forgarbage collection. In general, a chaotic update block, such as chaoticupdate block A 1004, allows sectors of data to be updated in a randomorder within a logical group, and with any repetition of individualsectors. The chaotic update block can be created by conversion from asequential update block when a sector of data written by a host islogically non-sequential to the previously written sector of data withinthe logical group being updated. All sectors of data subsequentlyupdated in this logical group are written in the next available sectorlocation in the chaotic update block, whatever their logical sectoraddress within the group.

Here, original block A 1002 and chaotic update block A 1004 includeinvalid and valid data, which is represented in FIG. 10A by a hatchedpattern and a dotted pattern, respectively. When a write command towrite new data 1001 is received, the non-volatile memory storage systemasserts a busy signal and then copies the valid data from original blockA 1002 and chaotic update block A 1004 to new block A 1006 until firstgarbage collection time period 1050 is reached. During copying, thenon-volatile memory storage system tracks the time, and the non-volatilememory storage system stops the copy operation before first garbagecollection time period 1050 is exceeded. As shown in FIG. 10A, thegarbage collection operation cannot be completed within first garbagecollection time period 1050 as there are still valid data remaining inoriginal block A 1002 and chaotic update block A 1004. As a result,after the portion of the valid data are copied to new block A 1006, newdata 1001 received before the garbage collection operation started arewritten to phased garbage collection block A 1008 before first timeoutperiod is reached.

FIG. 10B shows that the remaining portion of the garbage collectionoperation can be completed in a second timeout period. A second writecommand is received after the first write command. As a result, a secondtimeout period is allocated to the second write command. During thesecond timeout period, the remaining valid data are copied from originalblock A 1002 and chaotic update block A 1004 to new block A 1006. Here,all the remaining valid data (or last portion of the valid data) can becopied to new block A 1006 within second garbage collection time period1052. Accordingly, the garbage collection operation can be completedwithin the second timeout period. Since the garbage collection operationis completed in this second timeout period, original block A 1002 andchaotic update block A 1004 may be erased and made available for thestorage of additional data. After original block A 1002 and chaoticupdate block A 1004 are erased, new block A 1006 is converted into neworiginal block A 1010 and phased garbage collection block A 1008 isconverted into update block B 1012, which may or may not be associatedwith the new original block A. Since garbage collection operation iscompleted, another phased garbage collection block C 1014 is allocatedto store new data. As shown in FIG. 10B, if new data 1005 received fromthe second write command are in the same logical group as new data 1001,then the new data 1005 may be written to update block B 1012. However,as will be explained in more detail below, if new data 1005 are from adifferent logical group from new data 1001, then the new data 1005 arewritten to phased garbage collection block C 1014.

FIGS. 11A-11E are simplified block diagrams of memory blocks withchaotic update blocks being garbage collected in phases, in accordancewith another embodiment of the present invention. As shown in FIG. 11A,original block G 2002 and chaotic update block G 2004 are selected forgarbage collection when a write command to write new data 2012 isreceived. Here, original block G 2002 and chaotic update block G 2004include invalid and valid data, which is represented in FIG. 11A by ahatched pattern and a dotted pattern, respectively. After the writecommand is received, the non-volatile memory storage system asserts abusy signal and then copies the valid data from original block G 2002and from chaotic update block G 2004 to new block G 2008 until firstgarbage collection time period 2006 is reached. During copying, thenon-volatile memory storage system tracks the time, and the non-volatilememory storage system stops the copy operation before first garbagecollection time period 2006 is exceeded. As shown in FIG. 11A, thegarbage collection operation cannot be completed within first garbagecollection time period 2006 as there are still valid data remaining inoriginal block G 2002 and chaotic update block G 2004. As a result,after the portion of the valid data are copied to new block G 2008, newdata 2012 received before the garbage collection operation started arewritten to phased garbage collection block G 2010 before first timeoutperiod is reached.

FIG. 11B shows that the remaining portion of the garbage collectionoperation can be completed in a second timeout period. A second writecommand is received after the first write command. As a result, a secondtimeout period is allocated to the second write command. During thesecond timeout period, the remaining valid data are copied from originalblock G 2002 and chaotic update block G 2004 to new block G 2006. Here,all the remaining valid data (or last portion of the valid data) can becopied to new block G 2008 within second garbage collection time period2014. Accordingly, the garbage collection operation can be completedwithin the second timeout period. Since the garbage collection operationis completed in this second timeout period, original block G 2002 andchaotic update block G 2004 may be erased and made available for thestorage of additional data. Furthermore, new block G 2008 is convertedinto new original block G 2016 and phased garbage collection block G2010 is converted into update block H 2018. Since garbage collectionoperation is completed, another phased garbage collection block J 2020is allocated to store new data. If new data 2022 received from thesecond write command are in the same logical group as new data 2012,then the new data 2022 may be written to update block H 2018. However,in the example shown in FIG. 11B, new data 2022 and new data 2012 arefrom different logical groups. As a result, new data 2022 are written tophased garbage collection block J 2020 instead of update block H 2018.

Since phased garbage collection block J 2020 can store data from asingle logical group, the phased garbage collection block J may not beable to store new data that may be received in subsequent writeoperations. Therefore, a new garbage collection operation is performedduring second garbage collection time period 2014. As shown in FIG. 11C,another garbage collection operation is performed during the remainingtime left over in the second garbage collection time period. Here,original block K 2202 and chaotic update block K 2204 are selected forgarbage collection. Original block K 2202 and chaotic update block K2204 include invalid and valid data, which is represented in FIG. 11C bya hatched pattern and a dotted pattern, respectively. After thecompletion of the garbage collection operation shown in FIG. 11B, thenon-volatile memory storage system uses the remaining time (i.e.,remaining second garbage collection time period 2216) within the secondtimeout period to copy the valid data from original block K 2202 andchaotic update block K 2204 to new block K 2206. As shown in FIG. 11C,the garbage collection operation cannot be completed within remainingsecond garbage collection time period 2216 as there are still valid dataremaining in original block K 2202 and chaotic update block K 2204.

In FIG. 11D, a third write command is received after the second writecommand and a third timeout period is allocated to the third writecommand. Within third garbage collection time period 2236, a garbagecollection operation cannot be completed. New block K 2206 cannottherefore be converted into an update block. In this example, the newdata received from the third write command belong to a different logicalgroup from new data 2022, and do not have an open update block. Datafrom a single logical group can be stored in phased garbage collectionblock J 2020 but data from different logical groups cannot be stored inthe phased garbage collection block J. As a result, no blocks areavailable to store the new data received from the third write command.

In the example of FIG. 11D, when new data are received and there alreadyare data, such as new data 2022, stored in phased garbage collectionblock J 2020, then data in the phased garbage collection block J are tobe garbage collected before the new data from the third write commandcan be written or programmed. The third timeout period allocated to thecompletion of the third write command can be used for the garbagecollection operation. However, if third garbage collection time period2236 does not provide enough time to complete the garbage collectionoperation, then phased garbage collection block J 2020 is not empty andtherefore is not ready to receive or store new data from the third writecommand. Accordingly, the new data cannot be written within the thirdtimeout period and a timeout error will occur.

To accommodate the new data received from the third write command, FIG.11E shows the allocation of another phased garbage collection block,namely phased garbage collection block M 2212, for use in a garbagecollection operation in the third timeout period. If the remainingsecond garbage collection time period 2216 does not provide enough timeto complete the second garbage collection operation shown in FIG. 11C,then the non-volatile memory storage system may initially allocate twoor more phased garbage collection blocks. As shown in FIG. 11E, twophased garbage collection blocks, phased garbage collection block J 2020and phased garbage collection block M 2212, are initially allocated.With the additional allocated phased garbage collection block M 2212, ifthe garbage collection operation cannot be completed within thirdtimeout period, then new data 2214 received from the third write commandthat belong to a different logical group from new data 2022 may bestored in the phased garbage collection block M. As a result, new data2214 can be written within the third timeout period and a timeout errorwill not occur.

Use of a Scratch Pad Block as a Buffer

FIG. 12 is a flowchart diagram of detailed operations for performing aphased garbage collection with the use of a scratch pad block as abuffer, in accordance with an embodiment of the present invention. Asshown in FIG. 12, a write command is received in operation 1102 to writenew data to a memory. In an embodiment, the write command is a singlesector write command. In some circumstances, as will be explained inmore detail below, the write command can also be a multiple sectorswrite command, in accordance with another embodiment. After the writecommand is received, the non-volatile memory storage system asserts abusy signal in operation 1104.

Before the write command is executed, a portion of the garbagecollection operation is performed for a garbage collection time periodin operation 1106. For example, in an embodiment, one or more firstblocks are selected for garbage collection operation. The one or morefirst blocks can include invalid data and/or valid data. The valid dataare copied to a second block for a garbage collection time period.Depending on the garbage collection time period allocated to the garbagecollection operation and on the amount of valid data that are to becopied, all the valid data or a portion of the valid data are copied tothe second block. In an example, the garbage collection time periodallocated for the garbage collection operation can be expressed asGarbage collection time period=Timeout Period−Tprog  (2.0)where timeout period, as discussed above, is a fixed, limited period oftime. Tprog is the maximum programming time associated with writing thenew data to memory or is the maximum time the non-volatile memorystorage system takes to write the new data to the memory. As a result,in an embodiment, the non-volatile memory storage system tracks theamount of time for copying the valid data from the one or more firstblocks to the second block. The non-volatile memory storage system stopsthe copy before the time exceeds the garbage collection time period.

If the garbage collection operation cannot be completed by the garbagecollection time period, then the new data associated with the writecommand can be written to the scratch pad block in operation 1108. Itshould be appreciated that a scratch pad block is a form of data updateblock in which logical sectors within an associated logical group may beupdated in a random order and with any amount of repetition. The scratchpad block is created by a write command where the intended logicalsectors do not end or cross a physical page boundary. Since thenon-volatile memory storage system may not be able to program partialpages, sectors of a page can be temporarily stored in the scratch padblock. The non-volatile memory storage system accumulates sectors of thepage in the scratch pad block until all the sectors of the page arefilled with new data from various write commands. The non-volatilememory storage system then copies the full page (e.g., eight sectors ofnew data) from the scratch pad block to another block, such as an updateblock, in one program operation. Scratch pad block can therefore containpartial physical page worth of data. The scratch pad block can hold avalid page of new data for each update block in the non-volatile memorystorage system. Additionally, in an embodiment, the scratch pad blockcan hold one or more valid pages of new data that do not have updateblocks. The non-volatile memory storage system can have, for example,eight update blocks allocated and therefore, the scratch pad block canstore nine or more valid pages of new data. The non-volatile memorystorage system can write the new data to the scratch pad block before,during, or after the garbage collection operation. As will be explainedin more detail below, the new data may be copied from the scratch padblock to an update block upon completion of the garbage collectionoperation, once additional sectors of new data are received such thatthe physical page boundary is reached or crossed.

After the new data are written to the scratch pad block and the garbagecollection operation is performed for the garbage collection timeperiod, the non-volatile memory storage system releases the busy signalbefore the timeout period in operation 1110. Thus, the total time forexecuting the write command that includes one garbage collectionoperation or a portion of one garbage collection operation does notexceed the timeout period. If a portion of the garbage collectionoperation is performed within the timeout period, then the remainingportions are completed at subsequent timeout periods. When the garbagecollection operation is complete, the one or more first blocks beinggarbage collected are erased and made available for the storage ofadditional data.

FIGS. 13A and 13B are simplified block diagrams of memory blocks withsequential update blocks being garbage collected in phases, inaccordance with embodiments of the present invention. As shown in FIG.13A, original block A 1202 and associated sequential update block A 1204are selected for garbage collection. Original block A 1202 can includeinvalid and valid data, which is represented in FIG. 13A by hatchedpattern and dotted pattern, respectively. When a write command to writenew data 1210 is received, the write command may trigger the closure ofsequential update block A 1204, which is a type of garbage collectionoperation, because the new data are associated with a logical group thatdoes not have an open update block or because the new data result in theconversion of the sequential update block A to a chaotic update block.The non-volatile memory storage system asserts a busy signal and thencopies the valid data from original block A 1202 to sequential updateblock A 1204 until first garbage collection time period 1208 is reached.It should be noted that in addition to valid data from original block A1202, sequential update block A 1204 additionally includes existing data1205 that were written to the sequential update block A before thegarbage collection operation. During copying, the non-volatile memorystorage system tracks the time, and the non-volatile memory storagesystem stops the copy operation before first garbage collection timeperiod 1208 is exceeded. As shown in FIG. 13A, the garbage collectionoperation cannot be completed within first garbage collection timeperiod 1208 as there are still valid data remaining in original block A1202. As a result, after the portion of valid data is copied tosequential update block A 1204, new data 1210 are written to scratch padblock 1206.

FIG. 13B shows that the remaining portion of the garbage collectionoperation can be completed within a second timeout period. Here, asecond write command to write new data 1224 is received after the firstwrite command. As a result, a second timeout period is allocated to thesecond write command. During the second timeout period, the remainingvalid data are copied from original block A 1202 to sequential updateblock A 1204. In this example, all the remaining valid data (or lastportion of the valid data) can be copied to sequential update block A1204 within second garbage collection time period 1214. Accordingly, thegarbage collection operation can be completed within the second timeoutperiod. Since sequential update block A 1204 is filled, the sequentialupdate block A is converted to new original block A 1212 or a non-updateblock. Original block A 1202 is erased and can be made available for thestorage of additional data because the garbage collection operation iscompleted in this second timeout period. After original block A 1202 iserased, update block C 1222 is allocated and new data 1222 received fromthe second write command may be written to the newly allocated updateblock C. It should be noted that update block C 1222 may or may not beassociated with new original block A 1212.

After the garbage collection is completed within the second timeoutperiod, the non-volatile memory storage system may copy new data 1210stored in scratch pad block 1206 to update block C 1222 if there is timeavailable within the second timeout period. Scratch pad block 1206serves as a temporary buffer, as new data, such as new data 1210,written to the scratch pad block are later copied to another block(e.g., updated block C 1222). In the example of FIG. 13B, there is timefor copying new data 1210 from scratch pad block 1206 to update block C1222 within the second timeout period. New data 1210, which are storedin scratch pad block 1206, are in the same logical group as new data1224. Therefore, new data 1210 are copied to update block C 1222 afterthe completion of the garbage collection operation. New data 1210 storedin scratch pad block 1206 are marked as invalid and therefore,additional space in the scratch pad block could be made available forthe storage of additional new data. It should be noted that new data1210 and new data 1224 may belong to different logical groups. If newdata 1210 and new data 1224 belong to different logical groups, then newdata 1210 will remain in scratch pad block 1206. Once new data 1224 arewritten to update block C 1222, a new garbage collection operation maybe initiated within the second timeout period. A new update block (notshown) may therefore be allocated with the completion of the new garbagecollection operation and new data 1210 may be copied from scratch padblock 1206 to the new update block.

FIGS. 14A and 14B are simplified block diagrams of memory blocks withchaotic update blocks being garbage collected in phases, in accordancewith embodiments of the present invention. As shown in FIG. 14A,original block D 1302 and chaotic update block D 1304 are selected forgarbage collection. Here, original block D 1302 and chaotic update blockD 1304 include invalid and valid data, which is represented in FIG. 14Aby a hatched pattern and a dotted pattern, respectively. When a writecommand to write new data 1312 is received, the non-volatile memorystorage system asserts a busy signal and then copies the valid data fromoriginal block D 1302 and chaotic update block D 1304 to new block D1308 until first garbage collection time period 1306 is reached. Duringcopying, the non-volatile memory storage system tracks the time, and thenon-volatile memory storage system stops the copy operation before firstgarbage collection time period 1306 is exceeded. As shown in FIG. 14A,the garbage collection operation cannot be completed within firstgarbage collection time period 1306 as there are still valid dataremaining in original block D 1302 and chaotic update block D 1304. As aresult, after the portion of the valid data are copied to new block D1308, new data 1312 received before the garbage collection operationstarted are written to scratch pad block 1206 before the first timeoutperiod is reached.

FIG. 14B shows that the remaining portion of the garbage collectionoperation can be completed in a second timeout period. A second writecommand is received after the first write command. As a result, a secondtimeout period is allocated to the second write command. During thesecond timeout period, the remaining valid data are copied from originalblock D 1302 and chaotic update block D 1304 to new block D 1308. Here,all the remaining valid data (or the last portion of the valid data) canbe copied to new block D 1308 within second garbage collection timeperiod 1314. Accordingly, the garbage collection operation can becompleted within the second timeout period. Since the garbage collectionoperation is completed in this second timeout period, original block D1302 and chaotic update block D 1304 may be erased and made availablefor the storage of additional data. After original block D 1302 andchaotic update block A 1304 are erased, new update block E 1316 isallocated and new data 1314 received from the second write command arewritten to the newly allocated update block E. Again, new data 1314 arenot written to scratch pad block 1206 because an update block isavailable after the completion of the garbage collection operation andthere is no need to buffer the new data until a subsequent timeoutperiod. In this example, new data 1312 stored in scratch pad block 1206are copied to update block E 1316, assuming that new data 1312 and 1314belong to the same logical group.

Audio/Video Data

A host accessing data associated with audio/video files (hereinafter“audio/video data”) stored in a non-volatile memory storage system mayneed to write the audio/video data at a pre-determined rate of speedwhen compared to other data. As the host streams the audio/video data toand/or from the non-volatile memory storage system, the bandwidthallocated to the stream matches or exceeds the pre-determined rate ofspeed. A garbage collection operation performed during the access ofaudio/video data can degrade the write performance of the audio/videodata. Accordingly, in an embodiment, phased garbage collection isperformed when the multiple sectors write command is not associated withaudio/video data or the multiple sectors write command is at thebeginning of an audio/video write.

To distinguish audio/video data from other data, in an embodiment, thenon-volatile memory storage system can refer to the target logicaladdress associated with the multiple sectors write command. Sinceaudio/video data are written sequentially, a target logical address thatis translated as a backwards jump can indicate that the new data are notaudio/video data (or are the beginning of the audio/video data). Inanother embodiment, the non-volatile memory storage system can alsodistinguish audio/video data from other data by referring to the numberof sectors associated with the new data. Audio/video data can be storedin units referred to as recording units. The minimum recording unitlength associated with audio/video data can be 32 sectors. The number ofsectors associated with new data that is not an integer multiple of 32sectors can therefore indicate that the new data are not audio/videodata. New data received that do not align to, or do not start at thebeginning of a recording unit, also can indicate that the new data arenot audio/video data.

As a result, phased garbage collection can be performed if one of thefollowing conditions apply: (1) the multiple sectors write commandinvokes garbage collection operation; (2) the target logical address istranslated as a backwards jump; (3) the target logical address is notaligned to a recording unit boundaries; and (4) after the stop commandis received (i.e., end of the multiple sectors write command), if thenumber of sectors associated with the new data is not an integermultiple of 32.

FIG. 15 is a flowchart diagram of non-volatile memory storage systemoperations associated with a write command, in accordance with anembodiment of the present invention. The write command may be a singlesector write command where new data are written as single sectors torandom addresses across a memory cell array. Depending on host activityand card fragmentation, the host may write a long file with multiplesectors using single sector write commands to random locations. Sincethere is a limited number of update blocks allocated, these singlesector writes can exercise the update blocks rapidly, thereby can promptthe non-volatile memory storage system to perform garbage collectionoperations to clear blocks for subsequent write operations. The writecommand may also be a multiple sectors write command. Most new datawritten to the memory cell array are large data files occupying acontiguous sequential logical address space. Depending on host activity,the host may write the large data files using multiple sectors writecommands. Such new data comprises multiple sectors of new data withmultiple timeout periods. FIG. 7 shows an example of a multiple sectorswrite command. In general, since multiple timeout periods are availablewith a multiple sectors write command, the new data can be written to anallocated update block instead of the scratch pad block. Therefore, thescratch pad block is usually not used as part of the phased garbagecollection scheme in multiple write commands because the garbagecollection can usually be completed within the multiple timeout periodsallocated to the multiple sectors write command.

As shown in FIG. 15, a write command is received in operation 1402.Thereafter a determination is made in operation 1403 as to whether thewrite command is a single sector write command. If the write command isa single sector write command, a determination is made in operation 1404as to whether the single sector write command invokes a garbagecollection operation. If the single sector write command does not invokea garbage collection operation, then the new data are written to thememory in operation 1422. On the other hand, if the write command doesinvoke a garbage collection operation, then another determination ismade in operation 1408 as to whether a phased garbage collection ispending (i.e., a garbage collection operation that has already started,but was phased because the garbage collection could not be completed orif the phased garbage collection block is not empty). If there is phasedgarbage collection pending, then the phased garbage collection operationis continued or completed in operation 1410. In other words, theremaining portion from the previous garbage collection operation iscontinued. As shown in operation 1411, the phased garbage collectionoperation is performed until garbage collection time period (e.g.,difference between timeout period and programming time) or until thephased garbage collection operation is completed.

If the phased garbage collection operation can be completed withingarbage collection time period, then another determination is made inoperation 1412 as to whether the write command still invokes a garbagecollection operation, even after completing the phased garbagecollection operation. If the write command does not invoke a garbagecollection operation, then the new data are written to the memory inoperation 1422. On the other hand, if the write command does invokegarbage collection, then a garbage collection operation is performed inoperation 1414 until the garbage collection time period is reached inoperation 1418 or until the phased garbage collection is completed. Inan embodiment, if phased garbage collection block is used, then Equation1.0 discussed above can be used as the garbage collection time period.If the phased garbage collection operation cannot be completed withinthe garbage collection time period, then the new data may be written toone of the phased garbage collection blocks in operation 1420. Inanother embodiment, if the scratch pad block is used, then Equation 2.0discussed above can be used as the garbage collection time period inoperation 1418. If the phased garbage collection operation cannot becompleted within the garbage collection time period, then the new datamay be written to the scratch block in operation 1420. If the phasedgarbage collection operation can be completed within the garbagecollection time period, then the new data are written to the memory inoperation 1422.

It should be noted that if there is a phased garbage collection and thecurrent write command also invokes a garbage collection operation, thenthe garbage collection time period shown in operation 1418 is acontinuation of the garbage collection time period in operation 1410.Accordingly, if there is a phased garbage collection and the currentsingle sector write command invokes a garbage collection operation, thenboth operations are completed within the total garbage collection timeperiod. In other words, the execution time allocated for phased garbagecollection operations are shown in operation 1418 and garbage collectionoperation shown in operation 1410 can be, for example, the differencebetween the timeout period and the programming time.

After the new data are written to memory in operation 1422, adetermination is made in operation 1424 as to whether the new data areinteger multiples of 32 sectors. If the new data are integer multiplesof 32 sectors, then the new data may be associated with audio/video dataand the operation ends. However, if the new data are not integermultiples of 32 sectors, then a determination is made in operation 1426as to whether a phased garbage collection is pending. If there is phasedgarbage collection pending, then the phased garbage collection operationis continued or completed in operation 1428. If there is no phasedgarbage collection pending, then the operation ends.

Returning to operation 1402, a multiple sectors write command may alsobe received. With a multiple sectors write command, the sectors of newdata are stored (or buffered) and garbage collection operation can beperformed in operation 1452, if needed. The non-volatile memory storagesystem may not utilize a scratch pad block or a phased garbagecollection block to store new data in phased garbage collectionoperations because multiple timeout periods are allocated to themultiple sectors write command and one garbage collection operation canusually be completed by the end of the multiple sectors write command.Accordingly, instead of the scratch pad block, the non-volatile memorystorage system may store the new data in RAM associated with thenon-volatile memory storage system, or in other memories associated withthe non-volatile memory storage system, while asserting the busy signalsbetween sectors of new data in order to use the allocated timeoutperiods to perform garbage collection operations.

However, in an embodiment, the scratch pad block may be used in amultiple sectors write command if there are not enough timeout periodsallocated to complete the garbage collection operation. Here, adetermination can be made in operation 1454 as to whether less than Nsectors of the new data are received. A multiple sectors write commandwith at least N sectors of new data can be written directly to theupdate blocks and not to the scratch pad block. Here, N is defined as

$\begin{matrix}{N = {{RoundDown}.{to}.{Nearest}.{{Integer}\left\lbrack \frac{{Tgc} + {TO}}{TO} \right\rbrack}}} & (3.0)\end{matrix}$where TO is the timeout period and Tgc is the time period to perform onefull garbage collection operation. Such multiple sectors write commandcan be written directly to the update blocks and not to the scratch padblock. Equation 3.0 shows that new data are written to the scratch padblock as part of the phased garbage collection scheme, when the writecommand is a single sector write command or when the non-volatile memorystorage system receives less than N sectors of new data in a multiplesectors write command.

If less than N sectors are received, then the non-volatile memorystorage system operates the multiple sectors write command in accordancewith the single sector write command operations starting in operation1404. However, if more than N sectors of new data are received, then adetermination is made in operation 1456 as to whether a phased garbagecollection operation can be performed. If no phased garbage collectionoperation can be performed, then the new data are written to memory inoperation 1422. On the other hand, if a phased garbage collection can beperformed, then a phased garbage collection operation is performed inoperation 1422 until a time period of, for example, Tgc-Tprog. After thephased garbage collection operation, the new data are written to memoryin operation 1422.

The above-described embodiments provide methods and/or systems forphased garbage collection. A garbage collection operation can be splitinto multiple phases and the multiple phases are performed over multipletimeout periods. In phased garbage collection, the new data receivedfrom the write command may be stored in a phased garbage collectionblock or a scratch pad block. By splitting the garbage collectionoperation, each phase of the garbage collection operation can beexecuted within the timeout period and thereby prevent timeout errors.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the embodiments are notlimited to the details provided. There are many alternative ways ofimplementing the embodiments. Accordingly, the disclosed embodiments areto be considered as illustrative and not restrictive, and theembodiments are not to be limited to the details given herein, but maybe modified within the scope and equivalents of the appended claims. Inthe claims, elements and/or operations do not imply any particular orderof operation, unless explicitly stated in the claims.

1. A non-volatile memory storage system, comprising: a memory configuredto store a storage system firmware; a non-volatile memory cell array;and a processor in communication with the memory and the non-volatilememory cell array, the processor being configured to execute the storagesystem firmware stored in the memory, the storage system firmwarecomprising program instructions for, receiving a write command to writea plurality of data to the non-volatile memory cell array, asserting abusy signal, copying a portion of a plurality of valid data from one ormore first blocks of the non-volatile memory cell array to a secondblock of the non-volatile memory cell array for a garbage collectiontime period, writing the plurality of data to a phased garbagecollection block that spans a single logical group of the non-volatilememory cell array, converting the phased garbage collection block to anupdate block of the non-volatile memory cell array, and releasing thebusy signal before a timeout period.
 2. The non-volatile memory storagesystem of claim 1, further comprising erasing the one or more firstblocks.
 3. The non-volatile memory storage system of claim 1, whereinthe copying the plurality of valid data from the first and second blockscomprises: tracking a time for the copying the portion of the pluralityof valid data from the one or more first blocks to the second block; andstopping the copying the portion of the plurality of valid data beforethe time exceeds the garbage collection time period.
 4. The non-volatilememory storage system of claim 1, wherein the garbage collection timeperiod is a difference between the timeout period and a programming timeassociated with the writing the plurality of data.
 5. A non-volatilememory storage system, comprising: a read-only memory (ROM) configuredto store a storage system firmware; a non-volatile memory cell array;and a processor in communication with the ROM, the memory cell array,and the non-volatile memory cell array, the processor being configuredto execute the storage system firmware stored in the ROM, the storagesystem firmware comprising program instructions for, receiving a firstwrite command to write a first plurality of data to the non-volatilememory cell array, the first write command being allocated a firsttimeout period to complete an execution of the first write command,asserting a first busy signal, copying a first portion of a plurality ofvalid data from one or more first blocks of the non-volatile memory cellarray to a second block of the non-volatile memory cell array for agarbage collection time period, writing the first plurality of data to aphased garbage collection block that spans a single logical group of thenon-volatile memory cell array, releasing the first busy signal beforethe first timeout period, receiving a second write command to write asecond plurality of data to the non-volatile memory cell array, thesecond write command being received after the receiving the first writecommand, the second write command being allocated a second timeoutperiod to complete an execution of the second write command, asserting asecond busy signal, copying a second portion of the plurality of validdata from the one or more first blocks to the second block for thegarbage collection time period, converting the phased garbage collectionblock to a first update block of the non-volatile memory cell array,writing the second plurality of data to the first update block, andreleasing the second busy signal before the second timeout period. 6.The non-volatile memory storage system of claim 5, wherein the storagesystem firmware further comprises program instructions for erasing theone or more first blocks.
 7. The non-volatile memory storage system ofclaim 5, wherein the storage system firmware further comprises programinstructions for: allocating a fourth block; and writing the secondplurality of data to the fourth block.
 8. The non-volatile memorystorage system of claim 7, wherein the storage system firmware furthercomprises program instructions for copying a plurality of valid datafrom one or more fifth blocks to a sixth block for a remaining garbagecollection time period.
 9. The method of claim 8, wherein the pluralityof valid data are copied from the one or more fifth blocks to the sixthblock within the second timeout period.
 10. The non-volatile memorystorage system of claim 5, wherein the first and second write commandsare single sector write commands.
 11. A removable flash memory system,comprising: a host interface; a memory configured to store a storagesystem firmware; a non-volatile memory cell array; and a processor incommunication with the memory and the non-volatile memory cell array,the processor being configured to execute the storage system firmwarestored in the memory, the storage system firmware comprising programinstructions for, receiving a write command to write a plurality of datato the non-volatile memory cell array, asserting a busy signal,performing a portion of a garbage collection operation for a garbagecollection time period, writing the plurality of data to a phasedgarbage collection block that spans a single logical group in thenon-volatile memory cell array, converting the phased garbage collectionblock to an update block, and releasing the busy signal before a timeoutperiod.
 12. The non-volatile memory storage system of claim 11, whereinthe program instructions for performing the portion of the garbagecollection operation comprises program instructions for copying aportion of a plurality of valid data from one or more first blocks to asecond block for the garbage collection time period.
 13. Thenon-volatile memory storage system of claim 12, wherein the programinstructions for copying the portion of the plurality of valid datacomprises program instructions for: tracking a time for the copying theportion of the plurality of valid data from the one or more first blocksto the second block; and stopping the copying the portion of theplurality of valid data before the time exceeds the garbage collectiontime period.
 14. The non-volatile memory storage system of claim 11,wherein the write command is a single sector write command.
 15. Thenon-volatile memory storage system of claim 11, wherein the garbagecollection time period is a difference between the timeout period and aprogramming time associated with the writing the plurality of data. 16.A removable flash memory system, comprising: a host interface, aread-only memory (ROM) configured to store a storage system firmware; amemory cell array configured to maintain phased garbage collectionblocks that each span a single logical group in the non-volatile memorycell array; a non-volatile memory cell array; and a processor incommunication with the ROM, the memory cell array, and the non-volatilememory cell array, the processor being configured to execute the storagesystem firmware stored in the ROM, the storage system firmwarecomprising program instructions for, receiving a first write command towrite a first plurality of data to the non-volatile memory cell array,the first write command being allocated a first timeout period tocomplete an execution of the first write command, asserting a first busysignal, copying a first portion of a plurality of valid data from one ormore first blocks of the non-volatile memory cell array to a secondblock of the non-volatile memory cell array for a garbage collectiontime period, writing the first plurality of data to a phased garbagecollection block, releasing the first busy signal before a timeoutperiod, receiving a second write command to write a second plurality ofdata to the non-volatile memory cell array, the second write commandbeing received after the receiving the first write command, the secondwrite command being allocated a second timeout period to complete anexecution of the second write command, asserting a second busy signal,copying a second portion of the plurality of valid data from the one ormore first blocks to the second block for the garbage collection timeperiod, and converting the phased garbage collection block to an updateblock of the non-volatile memory cell array releasing the second busysignal before the second timeout period.
 17. The non-volatile memorystorage system of claim 16, wherein the storage system firmware furthercomprises program instructions for writing the second plurality of datato the phased garbage collection block.
 18. The non-volatile memorystorage system of claim 16, wherein the storage system firmware furthercomprises program instructions for writing the second plurality of datato an update block.
 19. The non-volatile memory storage system of claim16, wherein the storage system firmware further comprises programinstructions for erasing the one or more first blocks after the copyingthe second portion of the plurality of valid data.
 20. The non-volatilememory storage system of claim 19, wherein the one or more first blocksare erased if the second portion of the plurality of valid data is alast portion of the plurality of valid data.
 21. The non-volatile memorystorage system of claim 16, wherein the first and second write commandsare single sector write commands.